LISBON (Reuters) - Ukrainian President Volodymyr Zelenskiy said on Thursday his war-ravaged country needed more heavy weapons to defend itself from Russia's invasion that threatened its very survival, and asked Western nations to impose further sanctions.

       Speaking in a video address to the Portuguese parliament, he accused the Russian army of committing many atrocities in Ukraine, including in the port city of Mariupol, and asked Portugal to support a global embargo on Russian oil.

       He did not provide concrete evidence of the atrocities during the speech.

       Russia says it was forced to launch its "special military operation" to demilitarise and "denazify" Ukraine, and protect Russian-speakers there from "genocide" - arguments denounced by Kyiv and the West as baseless pretexts for war.

       (Reporting by Andrei Khalip and Catarina Demony)